I'm not sure I understand your post, but I think you are saying that ARCA should run the experiment and learn from it. Is that correct?

I agree with the concept of running experiments. However, I'm concerned about ARCA's approach. They are clearly doing things that don't make sense. Hanging objects in the rocket exhaust will reduce the effective thrust and it will produce random off-center thrust effects. Also, each tethered object will contribute to the frontal drag. It would be much more efficient to stack the stages in the conventional manner so there is a single frontal surface.

There is also the issue of whether it's possible to build a passive stabalization method. It depends on how "passive" is defined. If we are talking about usng only mechanical linkage, then it is possible. A perfectly balanced mass object could be used to position a gimballed rocket motor. The mass object would have to be perfectly isolated from any rotation of the rocket, and the gimballed rocket motor would reguire virtually no force to position it. ARCA's method is no where close to doing this.

Dave Not really, I'm hoping they will not choose this battle after all the good input and will save it for a more worthy one but at the same time if they must prove it to themselves then they must. And I'm making a statement about the well sometimes you just have to see it fail part to understand it. It was not very effective I take it, oh well I gave it a shot.

"Prove it to yourself if you really doubt (you could be right) whatever it takes ,but pick your battles wisely (weight the probability and the consequences). Learn from your mistakes and share what you learn."

Certainly ARCA wants to prove something but not to themselves. In their case, the all thing seems like " No one can prove we wrong then we ARE right". This kind of overconfidence may have some hidden reasons, yet unknown to us.We don't learn from our mistakes. After a mistake is done, the only positive occurrence may be that mistake won't occur again, but this tells nothing about another mistake that may appear. We learn from our successes. That team needs a success. They barely had one until now therefore they went for something that may draw maximum attention.

Since the force applied by a tether can only be in the direction of the tether, it doesn't matter how long the tether is. Therefore, the tether lengths can be reduced to zero. This results in a rigid rocket with the motor on the top, and this is not stable.

Actually, reducing the length to zero would result in a hinged rocket, not a rigid one. It may well fail, but your description of why is off the mark I think.

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

Actually, the cables may as well be solid rods. Attaching the cables just aft of the CP on the tow rocket and as close to the CG on the towed rocket (toward the tow rocket) would be beneficial (and as short as possible) Reducing the polar moment. It is still the rocket fallacy. With a twist It would be super easy to test with the F motor Dave Suggested. You could launch the whole stack for the test as I believe it will crash before the first stage finished its propulsion. Ozzy song "I'm going off the rails on this crazy train"For a price of say $200 I could run the test for you.

What about the effects of the air hitting the rocket? Wouldn't the rocket be stabilized because when the bottom starts to move off center, there is more air hitting it from the vertical, which will push it back to the center?

_________________“Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.” -Anonymous

Actually, reducing the length to zero would result in a hinged rocket, not a rigid one. It may well fail, but your description of why is off the mark I think.

I was thinking of the tethered masses as point objects, so reducing the tether lengths to zero would put all the tethered mass at the extended end of the first stage. However, you're correct that in reality it would be a hinged rocket since the tethered masses aren't point objects.

Actually, the cables may as well be solid rods. ... It would be super easy to test with the F motor Dave Suggested. You could launch the whole stack for the test as I believe it will crash before the first stage finished its propulsion. ... For a price of say $200 I could run the test for you.

Holy boomerang! Batman! See how the people are standing all around! They think it will go farther before becoming unstable! It came right back dident it! Not safe enough! Thanks for the video! Any response ARCA?

You could make the argument that the rocket in the video was only connected to the base in 2 points, and that it failed in the dimension that it wasn't connected in. So the video itself doesn't prove the point.

_________________“Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.” -Anonymous

It wont matter the rockets will fly similarly in fact identically. A very good demonstration of the rocket fallacy in action. ARCA are you still there? This should get your attention! So what do you think now? I'd just delete the whole thread and say "Thank you"

Your welcome Wish we had funding like that!I bet for $10k we could get the altitude record at least!The last guy's spent 10 times that? anybody noticing us at all?Monroe